In general, a fixing apparatus fixed to a palate during orthodontic treatment is used to move anterior teeth protruding to the front into the back of the mouth or into a specific direction.
In prior arts, a molar is used as such anchorage. More particularly, a predetermined bracket is attached to the molar and the teeth to be moved, and then, for example, a variety of archwire or an elastic material such as a spring or a rubber band, i.e., elastic chain, is connected to the bracket to ensure that the molar is fixed in place.
However, when the molar is used as an anchorage, the teeth to be moved is pulled by the molar acting as an anchorage (as an action) and simultaneously the molar is pulled from the teeth to be moved (as a reaction). Thus there is a problem of the movement of the molar, acting as an anchorage, to a certain extent.
A separate fixing apparatus, i.e., extra oral appliance, can be placed to prevent the movement of the anchorage. However, this can cause discomfort to a patient and thus there is a problem that treatment cannot be properly given without the patient's cooperation.
Therefore, recently, a method of placing a fixing apparatus to a bone in the palate, by inserting a screw, has been widely used. Namely, it comprises inserting the screw to the bone in the palate and attaching a predetermined bracket to the desired teeth to be moved, then connecting the brackets and the screw to an elastic material such as a spring or an elastic chain, or to a wire fixed to the bracket, and pulling with some force to move the teeth (usually the anterior teeth).
When the screw is inserted to the fixing apparatus and used as mentioned above, not only is movement of the molar prevented but the procedure is simplified and an effective orthodontic treatment can be achieved in a short amount of time. However, since there is no measure to hold the screw fixed in the fixing apparatus, it is difficult to place the fixing apparatus at an exact location due to movement of the screw to the left and right when implanting the screw to the palate through the fixing apparatus. Also, there is a problem of an inflammation or damage in the palate due to a large contact area between the palate and the fixing apparatus having a flat structure.